The present invention relates to lubricant of magnetic recording medium comprising perfluoropolyether, magnetic recording medium wherein the lubricant is employed and a magnetic recording device wherein the magnetic recording medium is applied.
Along with intense requirement of miniaturization and capacity enlargement of hard disk devices, high-density recording is earnestly pursued recently. In the head-disk system, the high-density recording is attained by shortening the distance between the magnetic head and the disk medium and by heightening the rotation speed of the disk medium.
However, the short distance and the high-speed rotation increase probability of high-speed contact of a slider mounting the magnetic head with the disk medium, and hence, various obstacles caused by frictional electricity charged in lubricant of the disk medium have become important problems. The most serious among them is a break of the head element caused by electric discharge generated between charged disk medium and the magnetic head.
This problem rarely occurs in a head-disk system wherein fly-up distance of the slider is sufficiently large or a conductive material such as aluminum is used as the substrate of the disk medium. However, it occurs frequently when the fly-up distance is small and a nonconductive substrate such as a glass substrate is used, and it becomes an important and inevitable problem in a contact type head-disk system wherein the slider does not fly.
As to the disk medium having aluminum substrate, sure grounding of the aluminum substrate is usually arranged so as to generate no potential difference between the disk medium and the head element for preventing electric discharge between them. Since depth of the lubricant film or the protection film on the disk surface is sufficiently thin, electric charge generated on the lubricant film can be conducted to the ground through the substrate and causes no potential difference between the lubricant film and the head element, even though the lubricant film or the protection film is not conductive.
However, in the disk medium having a glass substrate, for example, the electric charge generated on the disk surface remains there being unable to flow through the glass substrate.
When a certain conductive material can be applied to the lubricant for conducting the generated electric charge to the ground, the above problem should be effectively resolved, but such conductive lubricant does not seem to have been disclosed until now.